The subject matter disclosed herein relates to the art of rotary wing aircraft and, more specifically, to gearbox systems for rotary wing aircraft.
A gearbox system of a rotary wing aircraft transfers power from an engine, or multiple engines, for example, a turbine engine, to the rotor system. A typical system directs power from the engine to a single rotor system including a plurality of rotor blades. Since rotational velocity of the rotor is typically lower than the rotational velocity of the engine, the gearbox is used to reduce the rotational velocity of the turbine engine. Torque is subsequently increased through a series of intermediate gear stages and shafts, with an output velocity provided to the rotor system.
In other rotary wing aircraft with more complex rotor systems, the complexity of the gearbox typically also increases. For example, some rotary wing aircraft, such as the X2® helicopter produced by Sikorsky Aircraft Corporation, have two coaxial counter rotating main rotor assemblies. As such, the gearbox must be configured to transfer engine power to both rotor assemblies at the required directions of rotation, requiring two large final reduction stages. Further in X2®-type aircraft, the gearbox is further utilized to transfer power to a propeller assembly, typically located at a tail of the aircraft, to provide additional forward thrust. Consequently, the typical gearbox for such an aircraft is large and heavy.